We have been talking about electrons, which are particles, behaving like waves. your book discusses how x-ray diffractions provided evidence of this. find an image that shows the diffraction of electrons, insert that here, and explain how this proves it is behaving like a wave

the box does not move because you need to use a force greater than 300 n. you are only using 50 n. it needs to at least be 301 n for the box to move because then it is an unbalanced force and it will move the way that the greater force is pushing it. if you use only 300 n it will be a balanced force and will not move because the force you are exerting on the   box is the same as its force.

hope this !

im sorry if i went too in depth, i am going to include a link to a video on khan academy that will explain this.   hope that you like the video and that it explains more in detail to you.

that is the link.

tbh i don't know the answer for this question